1. Field of the Invention
The invention relates to a telecommunication system in which the sender types a word on the DTMF keypad, the system determines the identity of the word and, once the word is identified transmits the information in ASCII digital format on a packet transport network to a location near the receiver where it is converted into speech.
2. Description of Related Art
The prior art discloses some systems for using a DTMF keypad to transmit messages to a remote location where a speech synthesizer reproduces a word. Typical of such systems is the invention described in U.S. Pat. No. 4,307,266 entitled COMMUNICATION APPARATUS FOR THE HANDICAPPED. According to that invention a sender enters the appropriate position for the letter of the alphabet to be communicated. A second entry identifies which one of the plurality of letters is intended to be transmitted. The sending party has apparatus attached to the telephone set which decodes the two digit code entry and converts the two-digit code to a standard machine readable format which can be displayed on a standard output device such as an alphanumeric display or, for blind persons, a braille or similar output message. The sending party can transmit the message to the receiving party, by keying characters into a keyboard. Keyed-in characters are converted to speech by a speech synthesizer for transmission to the receiving party. In other words, the sender types in the word in DTMF code and the resultant is reproduced at the receiving station by synthesized voice. While the foregoing system may be useful for certain applications, it seems to be rather cumbersome, limited in its vocabulary, and relatively inefficient in its transmission mode.
Other patents that discuss use of DTMF codes for transmission purposes include U.S. Pat. Nos. 4,087,638; 4,427,848 and 4,608,460.
Some attempts have been made in the prior art to identify a word from a DTMF dial tone clue. A useful description of such techniques is found in an article entitled "Digital Techniques for Computer Voice Response: Implementations and Applications", Lawrence R. Rabiner, Fellow IEEE and Ronald W. Schafer, Senior Member, IEEE PROCEEDINGS OF THE IEEE, Volume 64, No. 4, April 1976.
Of more general interest is an article entitled "Alphabetic Data Entry Via the Touch-Tone Pad: A Comment", Sidney L. Smith and Nancy C. Goodwin, The Mitre Corporation, HUMAN FACTORS, 1971, 13(2) Page 189-190.
Of general interest also are the following items from the patent literature: U.S. Pat. Nos. 3,778,553; 3,967,273; 4,012,599; 4,191,854; 4,426,555; 4,532,378; 4,577,062; 4,585,908; 4,608,457 and 4,633,041 as well as the following British Patents: 1,320,895 and 1,320,896.
Whether taken individually or as a whole, none of the prior art appears to suggest the novel apparatus and method set forth in this disclosure for efficiently identifying a word typed on a DTMF keyboard and converting that word into ASCII digital format so that it can be efficiently transported via a packet transport network to a remote location where it is converted from data to speech.